U.S. patent application number 13/643072 was filed with the patent office on 2013-02-21 for storing and transport device and system with high efficiency.
The applicant listed for this patent is Gennaro De Michele, Mario Magaldi. Invention is credited to Gennaro De Michele, Mario Magaldi.
Application Number | 20130042857 13/643072 |
Document ID | / |
Family ID | 43127738 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130042857 |
Kind Code |
A1 |
Magaldi; Mario ; et
al. |
February 21, 2013 |
STORING AND TRANSPORT DEVICE AND SYSTEM WITH HIGH EFFICIENCY
Abstract
A device for storage and conveyance of thermal energy for an
energy production system apt to receive solar radiation and based
on the use of a modular fluidizable granular bed and a heat
exchanger associated thereto is described.
Inventors: |
Magaldi; Mario; (Salerno,
IT) ; De Michele; Gennaro; (Pisa, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Magaldi; Mario
De Michele; Gennaro |
Salerno
Pisa |
|
IT
IT |
|
|
Family ID: |
43127738 |
Appl. No.: |
13/643072 |
Filed: |
April 22, 2011 |
PCT Filed: |
April 22, 2011 |
PCT NO: |
PCT/IB11/51769 |
371 Date: |
October 23, 2012 |
Current U.S.
Class: |
126/617 ;
126/714 |
Current CPC
Class: |
Y02E 10/46 20130101;
F24S 60/00 20180501; F24S 20/20 20180501; Y02P 90/50 20151101; Y02E
10/40 20130101; F28D 13/00 20130101 |
Class at
Publication: |
126/617 ;
126/714 |
International
Class: |
F24J 2/34 20060101
F24J002/34 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2010 |
IT |
RM2010A000203 |
Claims
1. A device for storage and transfer of thermal energy, apt to
receive a solar radiation, which device comprises: a containment
casing; a bed of particles apt to store thermal energy, received
inside said containment casing; and at least one feed inlet for
feeding a fluidization gas through said bed of particles, the
overall arrangement being such that, in use, such fluidization gas
moves the particles of said bed causing or fostering a heat
exchange between the particles and pipe bundles in which a working
fluid flows.
2. The device according to claim 1, wherein the particles of said
bed are made of a granular material of a substantially regular
shape, preferably a spherical shape.
3. The device according to claim 1, wherein the particles of said
bed have dimensions of the order of about 50-200 micron.
4. The device according to claim 1, comprising a compartmenting of
the fluidization area, apt to allow a selective and/or
differentiated fluidization of one or more portions of said bed of
particles by the fluidization gas.
5. The device according to claim 1, further comprising a further
storage means in the form of a monolithic block.
6. The device according to the claim 5, wherein said storage block
is of graphite or comprises graphite.
7. The device according to claim 5, wherein said storage block is
obtained by compaction of a material in granular form.
8. The device according to claim 1, further comprising a further
storage means in the form of a further fluidizable bed of particles
received inside said containment casing, said beds of particles
being preferably arranged one concentrically to the other.
9. The device according to claim 1, having one or more receiving
cavities inside which or inside each of which the solar radiation
is concentrated.
10. The device according to claim 9, comprising a plate of a
substantially transparent material, preferably quartz, arranged in
correspondence of the mouth of said or each cavity.
11. The device according claim 10, wherein said or each plate is
permeable to the solar radiation entering into the respective
cavity and impermeable to infrared radiation going out from the
latter.
12. The device according to claim 9, comprising a secondary solar
radiation concentrator, placed at the inlet of said or at least one
receiving cavity
13. The device according to claim 9, wherein said further storage
means is arranged immediately in correspondence of said or at least
one of said cavities.
14. The device according to claim 9, wherein said bed of particles
is arranged immediately in correspondence of said or at least one
of said cavities.
15. The device according to claim 1, having an outflow duct for the
fluidization gas.
16. The device according to claim 1, comprising one or more heat
exchanging elements which receive or are apt to receive a working
fluid and are arranged so as to be in contact with said bed of
particles and/or so as to be touched, in use, by said bed when the
latter is fluidized by said fluidization gas.
17. A plant for producing steam or heat for industrial uses,
comprising one or more devices according to claim 1.
18. The plant according to claim 17, comprising means for feeding
the fluidization gas through at least one inlet of said device.
19. The plant according to claim 18, wherein said feeding means
comprises means for the forced circulation of the fluidization
gas.
20. The plant according to claim 18, wherein said feeding means is
selectively controllable to change the velocity of the fluidization
gas.
21. The plant according to claim 17, comprising means for
de-pulverizing the fluidization gas.
22. The plant according to claim 17, comprising means for a
selective feeding of the fluidization gas to selected portions of
said bed of particles.
23. The plant according to claim 17, comprising means for feeding a
combustion gas inside said casing of said device.
24. The plant according to claim 17, which is an electrical power
generating plant.
25. A method of storage and subsequent exchange of thermal energy
of solar origin, providing the use of a bed of particles apt to
receive and store thermal energy of solar origin, and a
fluidization of said bed of particles such as to cause or foster a
thermal exchange between the latter and the pipe bundles of a heat
exchanger.
26. The method according claim 25, wherein said fluidization is
carried out by a controlled feeding of a fluidization gas,
preferably air.
27. The method according to claim 25, providing a differentiated
fluidization of selected portions of said bed of particles.
28. The method according to claim 25, wherein a working fluid,
which is water and/or steam, runs in said pipe bundles.
29. The method according to claim 25, providing a step of storing
thermal energy in a storage means during sunlight hours and a step
of heat transfer from said means to the pipe bundles by
fluidization of the bed of particles in the absence of solar
radiation.
30. The method according to claim 25, providing the use of one or
more devices or of a plant.
31. The method according to claim 25, providing a combustion of
gaseous fossil fuel inside said bed of particles of said
device.
32. The method according to claim 25, providing a step of storing
thermal energy and of concomitant or deferred transfer of said
energy to the heat exchanger, in order to obtain a constant
generation of energy.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a device for storage and
transport of thermal energy, in particular of solar origin,
preferably for a subsequent or concurrent use of the same for the
production of electric energy.
BACKGROUND OF THE INVENTION
[0002] It is known to store solar energy, for subsequent use,
concentrated by heliostats, fixed or tracking, within a receptor
consisting of a block of material having a high thermal
conductivity (typically graphite). Such block generally carries a
suitably oriented cavity whereon said heliostats are directed. The
receptor block, moreover, is typically associated to a heat
exchanger having pipe bundles immersed in the same block and
crossed by a working fluid--or carrier fluid, typically water, at
the liquid or vapor state at a high temperature. The heat stored in
the receptor block is transferred to such working fluid in order to
produce vapor or heat for industrial plants.
[0003] In a system for storing solar energy in graphite block of
the type described above, the temperatures involved may range from
400.degree. C. to 2000 .degree. C. The upper temperature limit is
bound by the thermal resistance of the heat exchanger, and in
particular the metal pipe bundles thereof. In particular, in
relation to the temperature difference between the incoming fluid
and the exchanger pipes, the thermo-dynamic conditions of the fluid
may change so quickly as to create strong stresses of the pipe
metal (thermal and mechanical shocks), such as to subject the heat
exchangers to extreme physical conditions, with the risk of
excessive internal tensions and subsequent breakage.
[0004] Moreover, a difficulty of the systems described is to ensure
continuity in the amount of heat removed by the accumulator, since
the storage step is linked to the atmospheric conditions and to the
day/night cycles. Known systems therefore are little versatile in
terms of capability of adaptation to the downstream energy
requirements.
[0005] In general, moreover, known systems are not optimized in
terms of usage efficiency and conversion of the incoming electric
energy.
SUMMARY OF THE INVENTION
[0006] The technical problem at the basis of the present invention
therefore is to overcome the drawbacks mentioned with reference to
the prior art.
[0007] The above problem is solved by a device according to claim
1, by a plant, preferably for energy production, comprising the
same and by a method according to claim 25.
[0008] Preferred features of the invention are contained in the
dependent claims.
[0009] An important advantage of the invention consists in that it
allows obtaining a storage of thermal energy of solar origin in an
efficient and reliable manner, minimizing the thermal stresses of
the exchangers and increasing the thermal exchange efficiency to
the carrier fluid, thanks to the use of a fluidizable granular bed
that can carry out a dual function of heat storage and thermal
carrier. At the basis of such use, there are the favorable features
of thermal exchange of the fluidized beds and the effective
convective conveyance of the heat subsequent to the mobility of the
granular phase. Both these features are linked to the possibility
of imparting a rheological behavior to a granular solid that is
comparable to that of a fluid, actually thanks to the fluidization
thereof.
[0010] Moreover, thanks to the possibility of controlled and
selective fluidization of the granular storage means, a better
continuity of heat extraction and an optimized capability of
adaptation to the downstream energy requirements are ensured.
[0011] Moreover, a greater flexibility in energy production is
possible by burning gaseous fuel inside the fluidized bed, as shall
be better explained in the detailed description of preferred
embodiments made hereinafter.
[0012] Further advantages, features and the methods of use of the
present invention will appear clearly from the following detailed
description of some embodiments thereof, illustrated by way of a
non-limiting example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Reference shall be made to the figures of the annexed
drawings, wherein:
[0014] FIG. 1 shows a diagram of a system incorporating a preferred
embodiment of a device for storage and conveyance of thermal energy
according to the invention, provided with a single receiving
cavity;
[0015] FIG. 1a shows a plan view of the device of FIG. 1, showing
the modularity of a fluidizable bed of particles of the same
device;
[0016] FIG. 2 shows a diagram of a system relating to a first
embodiment version of the device of FIG. 1, provided with multiple
receiving cavities;
[0017] FIG. 3 shows a diagram of a system relating to a second
embodiment version of the device of FIG. 1, wherein the fluidizable
bed of particles is directly exposed to a receiving cavity and a
further block storage means is provided, arranged at the periphery
of said fluidizable bed;
[0018] FIG. 4 shows a diagram of a system relating to a third
embodiment version of the device of FIG. 1, wherein the fluidizable
bed of particles is directly exposed to multiple receiving cavities
and a further fluidized bed is provided for transferring the heat
to the pipes of an exchanger;
[0019] FIG. 5 shows a diagram of a system relating to a fourth
embodiment version of the storage device of FIG. 1, having a dual
fluidizable bed as in FIG. 4 but with a single central receiving
cavity; and
[0020] FIG. 6 shows a device of the type shown in the previous
figures inserted in a system not provided with a combustion of fuel
gas and that has a closed circuit of a fluidization gas.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] With reference first to FIGS. 1 and 1a, a device for storage
and transfer of thermal energy according to a preferred embodiment
of the invention is shown, by way of example, as inserted in a
plant for the production of electric energy globally indicated with
reference numeral 100.
[0022] System 100 comprises one or more devices for storage and
transfer of thermal energy, one of which is globally indicated with
reference numeral 1 (for simplicity, FIG. 1 only shows one
device).
[0023] Device 1 is apt to store the thermal energy that originates
from a solar radiation conveyed/concentrated thereon for example by
fixed or tracking heliostats.
[0024] Device 1 comprises a containment casing 2 preferably of
metal and thermally insulated therein so as to minimize the heat
dispersion to the outside environment.
[0025] Casing 2 carries a cavity 20 wherein the solar energy is
concentrated.
[0026] One feed inlet 21 is obtained onto casing 2 for a
fluidization gas, the role of which shall be clarified later
on.
[0027] At a top portion of casing 2, device 1 is provided with an
outflow duct 5 for the fluidization means, the role of which shall
also in this case be clarified later on.
[0028] In the present example--and as is better shown in FIG.
1a--device 1 has an overall cylindrical geometry, with cavity 20
arranged centrally and having a cap-wise development.
[0029] A storage means 30 is arranged within casing 2, preferably
shaped as a monolithic graphite block or comprising graphite and
obtained for example by compaction of granular material. In the
present embodiment, the storage means 30 is arranged just at cavity
20, so as to define the peripheral walls thereof and therefore be
directly impinged by the solar radiation concentrated in the same
cavity 20.
[0030] At the inlet of cavity 20 there may be arranged a plate 13
of a substantially see-through material, preferably quartz.
Preferably, plate 13 is suitably treated so as to be permeable to
solar radiation entering into the cavity and impermeable to
infrared radiation going out therefrom. Plate 13 therefore has the
function of insulating the receiving cavity 20 from the outside
environment, minimizing the losses for radiation from within device
1.
[0031] The walls of cavity 20 may also have a metal coating 31 or
an equivalent coating--shown in a purely schematic manner in FIG.
1--that preserves the storage means 30 from oxidation and
optionally retains a possible dispersion of fine particles coming
from the same storage means, for example if graphite subject to
dusting is used.
[0032] Variant embodiments may provide for a different material for
the above storage block 30, provided it has high thermal
conductivity and capability that allow a quick heat diffusion
within the same block and a maximization of the amount of heat
stored.
[0033] Within casing 2 and circumscribed to the monolithic storage
block 30 there is provided, according to the invention, a
fluidizable bed of particles, globally indicated with reference
numeral 3. The particles of bed 3 are also apt to the storage of
thermal energy and are made of a material suitable for thermal
storage and according to preferred features described later on.
[0034] The pipe bundles 4 of a heat exchanger, which in use are run
through by a working fluid, are arranged within the bed of
particles 3, or in the proximity thereof.
[0035] As mentioned above, the inlet 21 of device 1 is suitable for
allowing the inlet into casing 2--and specifically through the bed
of particles 3--of a fluidization gas, typically air. In
particular, the overall arrangement is such that the gas can move
the particles of bed 3 so as to generate a corresponding
flow/motion of particles suitable for heat exchange between the
particles and the pipe bundles 4.
[0036] At inlet 21 there is provided a distribution septum of the
fluidization gas, suitable for allowing the inlet of the latter
while ensuring a support for the bed of particles 3.
[0037] A dust separator 6, typically with inertial impactors or
equivalent devices with low load losses and cyclone operation, is
placed in line with the outflow duct 5 and de-pulverizes the outlet
gas returning the particles separated from the gas within casing
2.
[0038] The position of the pipe bundles 4 relative to the bed of
particles, or better the exposure of the pipe surface relative to
the bed of particles, is such as to maximize the amount of heat
exchanged, the latter being proportional to the product of the
thermal exchange coefficient and of the surface involved in the
same thermal exchange.
[0039] The pipe bundles 4 may be immersed or partly immersed in the
bed of particles 3 (as in the example of FIG. 1) or facing it. The
choice depends upon the management modes to be used for the device
and upon the minimum and maximum height of the bed of particles
upon the variation of the fluidization gas speed. In particular, as
such speed increases, the surface of the pipe bundle involved in
the thermal exchange increases.
[0040] As is shown in FIG. 1a, the bed of particles 3 is preferably
divided into multiple sections, optionally by partitions 330,
having a modular structure that allows a selective fluidization
thereof, by a compartmenting of the fluidization area and gas
feeding only at bed portions selectable according to the specific
operating requirements.
[0041] The feeding of the fluidization gas to inlet 21 of device 1
takes place by feeding means of plant 100 which comprises feed
ducts 210 connected to forced circulation means 8, typically one or
more fans. In particular, the feeding means defines a circuit that
collects the gas, preferably air from the environment, which enters
inlet 21 of device 1 and downstream thereof, through duct 5, to the
de-polverising means 6 and to an exchanger 7 for pre-heating the
working fluid. A manifold 14, or air case, is further provided, for
the inlet of the fluidization gas.
[0042] The feeding means may be selectively controlled for varying
the fluidization gas speed and thus the overall thermal exchange
coefficient between the particles of bed 3 and the pipe bundles
4.
[0043] In fact, by changing the gas crossing speed it is possible
to control and modify the overall thermal exchange coefficient of
the fluidized bed towards the storage block and the working fluid,
with consequent flexibility in the adjustment of the amount of
thermal power transferred. This effect is especially useful for
adjusting the amount of heat transferred from the storage means to
the working fluid through the bed of particles, due to the solar
radiation conditions depending on the load required.
[0044] The fluidization condition of the bed of particles is
preferably boiling, or in any case such as to maximize the thermal
exchange coefficient and minimize the conveyance of fine particles
in the fluidization gas. To this end, the choice of the bed
particle material is based on the thermal features of high thermal
conductivity and diffusivity of the material constituting the same
particles and in particular on the low abrasiveness to meet the
need of minimizing the erosion phenomenon of both the storage block
and the particles of the same bed, so as to limit the production
and conveyance of fine particles into the fluidization gas. Based
on these remarks, a preferred configuration privileges the use, for
the particles of bed 3, of granular material inert to oxidation,
with regular shape, preferably spheroid and/or preferably of
dimension within the range of 50-200 microns; and such that said
dimension preferably are native, that is, not resulting from the
aggregation of smaller sized particles.
[0045] When needed, it is possible to provide a surface of a high
thermal conductivity material 32 to protect the portion of storage
block involved in the action of the bed of granular material.
[0046] As regards the working fluid, in the present example and in
the preferred configuration, this is water that crossing the pipe
bundles 4 and by the effect of the heat exchanged in the fluidized
bed, vaporizes.
[0047] The circuit of the working fluid is provided with ducts 90
that define the pipe bundles 4 within device 1, and in the example
given in FIG. 1 they provide a steam turbine 10 connected to an
electric energy generator, a condenser 11, a feeding pump 12 and
the heat exchanger 7 that acts as pre-heater.
[0048] The entire device 1 is thermally insulated and if the
material(s) constituting the storage block 30 and/or the bed of
particles 3 is/are not inert to air (that is, can undergo oxidation
phenomena), it is necessary to evacuate the air from the inside
environment of device 1 and/or a light over-pressure of the inside
environment obtained with an inert gas. In that case, the
fluidization gas of the bed of particles must be inert and the
feeding circuit of said gas is closed, as shown in FIG. 6.
[0049] Device 1 is provided with a system for closing the receiving
cavity (system not shown in the figure), thermally insulated, which
prevents the dispersion of thermal energy from the same cavity to
the outside environment. Such closing system, optionally automatic,
is actuated overnight.
[0050] In a variant embodiment, the storage device 1 is associated
with a secondary reflector/concentrator, not shown in the figures,
positioned at the inlet of cavity 20 and thus around the inlet of
casing 2 which allows access of the radiation concentrated by the
heliostats.
[0051] Such secondary reflector, thanks to an inside mirror surface
suitably shaped for example with a parabolic or hyperbolic profile,
allows recovering a part of the reflected radiation that would not
reach cavity 20. In fact, a part of the radiation reflected by the
heliostats, for reasons due to imperfections of the surfaces and/or
aiming of the same, does not enters into the cavity inlet and would
therefore be lost.
[0052] A possible alternative would consist in obtaining a wider
inlet of the cavity: however, this solution would considerably
increase the radiation of the same cavity towards the outer
environment, with the result of losing a considerable part of the
power. The use of a secondary concentrator also allows releasing
the design bounds as regards the accuracy of the heliostat bending,
which causes a variation of the dimension of the beam reflected on
the receiver. Moreover, the use of said secondary concentrator
allows using flat heliostats, with an area not exceeding the inlet
surface. This aspect greatly influences the total technology cost:
flat mirrors are very inexpensive and the cost of the heliostats
typically represent over half the total cost of a system.
[0053] The orientation of the local concentrator described
hereinabove follows the orientation and the position of the cavity
facing the heliostat field.
[0054] The joint use of the already mentioned quartz plate 13, or
other see-through material, and of the secondary concentrator,
arranged at the inlet of the receiving cavity, is particularly
advantageous as they both contribute to increasing the absorption
factor of the available solar energy.
[0055] Based on another variant embodiment referred to in FIG. 2,
the device of the invention--herein indicated with reference
numeral 102 and inserted in a plant 101--may be provided with
multiple receiving cavities, two cavities 201 and 202 being shown
in the figure for the example described. The presence of multiple
receiving cavities allows mitigating the thermal flows that affect
the inside walls of the single cavity and lowering the working
temperatures, increasing the competitiveness and the performance of
the materials used as cavity coating. In this case, the features
described above with reference to the embodiment of FIGS. 1 and 1a
for the single cavity 20 are the same for each cavity 201 and
202.
[0056] Unlike the storage device described with reference to FIG.
1, device 102 provides for the bed of particles 3 to be arranged
centrally and for the monolithic or granular storage block,
indicated with reference numeral 301, to be arranged laterally to
the bed.
[0057] Along the line of the working fluid of plant 101 there is
arranged a degasser 40 with tapping to turbine 10 and, upstream
thereof, an extraction pump 120 or an equivalent means.
[0058] For the rest, device 102 and system 101 are similar to those
already described with reference to FIG. 1.
[0059] With reference to FIG. 3, a further variant embodiment of
the device of the invention, indicated with reference numeral 104
and inserted in a system 103, provides for the granular material
constituting the fluidizable bed 3 to receive the solar thermal
energy directly from the surfaces of the receiving cavity 20 and
therefore to serve as storage means besides to serving as thermal
carrier. Any possible additional storage material, indicated with
reference numeral 300, may be positioned at the periphery of the
fluidizable bed. In this configuration the bed of particles, when
fluidized, withdraws thermal energy from the walls of the receiving
cavity and transfers it to both the pipe bundle 4 of the heat
exchanger and to the surfaces of the storage means 300, if
provided. As already said, the heat transfer speed, that is, the
thermal exchange coefficient is regulated by the fluidization air
speed.
[0060] In the presence of solar radiation, the solar energy is
concentrated to cavity 20 and, by the fluidization of the bed of
particles, the thermal energy is partly transferred to the pipes of
exchanger 4 and partly to the storage means 300. The heat transfer
direction is from cavity 20 to the bed of particles 3 and hence to
exchanger 4 and to the storage means 300, the same being at a lower
temperature than the granular material 3 and in direct contact with
cavity 20.
[0061] In the absence of solar energy, for example overnight, by
fluidizing the bed of particles 3 the heat passage takes place from
the storage means 300 to the particles of bed 3 and hence to pipes
4 of the exchanger, ensuring continuity of operation and steam
dispensing and thus, of thermal power from the device. Thus, in the
absence of solar energy concentrated to the receiving cavity 20,
the heat transfer direction reverses from the storage means, which
has stored thermal energy transferred through the fluidization of
the bed of particles during the insulation hours, towards the
particles of the same bed, that is, towards the heat exchanger
pipes.
[0062] For the rest, device 104 and system 103 of FIG. 3 are
similar to those already described with reference to FIGS. 1 and
2.
[0063] With reference to FIG. 4, a further variant embodiment of
the device of the invention, indicated with reference numeral 106
and inserted in a plant 105, is provided with a first and a second
fluidizable bed, respectively indicated with reference numerals 304
and 305, arranged the first one concentrically to the second one,
and with the function of storage means and thermal carrier,
respectively.
[0064] Always with reference to FIG. 4, the granular material
constituting the first fluidizable bed 304 receives the solar
thermal energy directly from the surfaces of the receiving
cavities, here indicated with reference numerals 203 and 204, and
thus serves as storage means. The heat transfer, on the other hand,
is carried out by the second fluidizable bed 305 arranged within
the first one 304 and wherein pipes 4 of the heat exchanger are
seated. This configuration allows greater system flexibility both
in the storage step and in the heat release to the carrier fluid,
thanks to the possibility of acting independently on the actuation
and on the speeds of the fluidization gas of the two beds of
granular material and/or of sections of the same. A similar
configuration is that of the version shown in FIG. 5, wherein the
position of the two beds, that is, storage and carrier, is reversed
compared to the case of FIG. 4, since in FIG. 5 a single receiving
cavity 205 is provided in central position.
[0065] As already mentioned, the fluidized beds may also be not
separated by physical partitions 330, but by individually actuating
modular zones through the compartmenting of the fluidization
gas.
[0066] For any of the described configurations, the sizing of the
device, and in particular that of the granular bed, the
fluidization gas speed range, the amount of storage means (solid or
granular) optionally associated to the fluidized bed, as well as
the surfaces of the heat exchanger, are such as to ensure the
storage of thermal energy during sunlight hours and conveyance
thereof overnight to the heat exchanger through the fluidization of
the bed particles.
[0067] Moreover, as already mentioned, for any of the
configurations described using a modular structure of the fluidized
bed and modulating the fluidization speed of the same particles for
each section it is possible to regulate the amount of thermal
energy transferred to the pipes, choosing to use one or more
sections for storage or heat transfer by a selective and/or
differentiated fluidization thereof, ensuring continuous operation
of the device of the invention.
[0068] Furthermore, with plants provided with multiple devices of
the invention, as illustrated so far, the possibility of regulating
the amount of heat transferred to the exchanger for each device and
required for keeping the temperature and pressure of the steam
produced constant allows the advantage of maintaining, decreasing
or increasing the energy production.
[0069] In the case of systems based on multiple devices, the sizing
of the same and the operating logic are coordinated for obtaining a
predetermined production of energy even in the absence of solar
radiation.
[0070] In the above description, reference has been made by way of
an example to the application of the device to a stand-alone system
for the production of electric energy. However, it shall be
understood that the possible applications of the device are wide
and related to the production of steam or heat for industrial
systems such as thermoelectric plants, salt removing systems,
tele-heating and so on.
[0071] The law provisions that regulate the production of energy
from renewable sources allow for a minimum share of the same energy
to be produced by combustion of fossil fuels. Usually, in the prior
art devices this operation is carried out in production units
separate from the main production system.
[0072] On the contrary, an important advantage of energy production
plants based on the device of the invention is the possibility of
burning gaseous fossil fuel inside the fluidized bed.
[0073] For this reason, for each one of the embodiments described
herein with reference to the respective FIGS. 1-3, these latter
figures show an inlet of combustion gas 401 at the fluidizable bed
that acts as thermal carrier and directly at the fluidization gas
feeding channels.
[0074] For the variants of FIGS. 4 and 5, such feeding of
combustion gas may be provided, as shown, for one or both the
fluidizable beds.
[0075] All the figures related to the description show a
schematization of the configurations and, as such, they may not
show components such as valves or sensors, etc. which must be
provided for the conventional regulation of fluid circuits.
[0076] At this point, it shall be better understood that the
fluidized bed system has the dual advantage of high thermal
exchange coefficients at the bed-storage means or bed-bed interface
and at the pipe surfaces immersed in the granular bed, besides a
high thermal "diffusivity" of the same granular bed, an essential
property in relation to the possibility of quickly
charging/discharging the thermal accumulator in the transitory
operating steps.
[0077] The invention therefore allows a thermal energy storage
within the particle bed and the variation of the thermal power in
output from the system by modulating the fluidization speed of the
same particles.
[0078] Also the use of multiple cavities suitably sized and
oriented towards the mirror field allows reducing the incident
thermal flows and mitigating the maximum temperatures that would
affect the single cavity, making the choice of coating technologies
and materials for the walls of the same cavity more
competitive.
[0079] The modular structure of the fluidized bed then allows
actuating one or more sections with considerable management margins
and makes the system availability less dependent on both the
atmospheric conditions and on the availability of the energy
generator.
[0080] Moreover, the concurrent combustion of fuel gas within the
fluidized bed of the device allows keeping the system energy
production constant even in low insulation periods.
[0081] Finally, it shall be understood that the invention also
provides a method for storage and heat exchange as defined in the
following claims and having the same preferred features described
above with reference to the various embodiments and versions of the
device and of the plant of the invention.
[0082] The present invention has been described so far with
reference to preferred embodiments. It is understood that other
embodiments may exist that relate to the same inventive scope, as
defined by the scope of protection of the following claims.
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